U.S. patent number 9,845,804 [Application Number 14/398,039] was granted by the patent office on 2017-12-19 for positive displacement pump assembly with movable end plate for rotor face clearance control.
This patent grant is currently assigned to Eaton Corporation. The grantee listed for this patent is EATON CORPORATION. Invention is credited to Daniel R. Ouwenga, Brian T. Smith.
United States Patent |
9,845,804 |
Ouwenga , et al. |
December 19, 2017 |
Positive displacement pump assembly with movable end plate for
rotor face clearance control
Abstract
A positive displacement pump assembly includes a rotor housing
defining a rotor cavity, and an end plate configured to at least
partially close one end of the rotor cavity. Rotors are supported
on and fixed to rotor shafts and extend through the rotor cavity. A
first pair of bearings fixing the rotor shafts to the end plate. A
second pair of bearings fixes the rotor shafts to the rotor
housing, preventing relative axial movement between the rotor
shafts and the rotor housing. The end plate is axially movable with
the rotor shafts when the rotor shafts vary in axial length due to
thermal fluctuations so that changes in an axial clearance at end
faces of the rotors are reduced.
Inventors: |
Ouwenga; Daniel R. (Cleveland,
OH), Smith; Brian T. (Cleveland, OH) |
Applicant: |
Name |
City |
State |
Country |
Type |
EATON CORPORATION |
Cleveland |
OH |
US |
|
|
Assignee: |
Eaton Corporation (Cleveland,
OH)
|
Family
ID: |
48521399 |
Appl.
No.: |
14/398,039 |
Filed: |
April 29, 2013 |
PCT
Filed: |
April 29, 2013 |
PCT No.: |
PCT/US2013/038589 |
371(c)(1),(2),(4) Date: |
October 30, 2014 |
PCT
Pub. No.: |
WO2013/165876 |
PCT
Pub. Date: |
November 07, 2013 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150118094 A1 |
Apr 30, 2015 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
61640330 |
Apr 30, 2012 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01C
21/108 (20130101); F04C 29/005 (20130101); F04C
18/16 (20130101); F04C 27/006 (20130101); F04C
2240/52 (20130101); F04C 2270/17 (20130101) |
Current International
Class: |
F01C
19/08 (20060101); F04C 18/16 (20060101); F04C
29/00 (20060101); F01C 21/10 (20060101); F04C
27/00 (20060101); F04C 15/06 (20060101); F01C
19/10 (20060101) |
Field of
Search: |
;418/133,105-108,132,134,206.1,206.4,206.7,206.6,73,130,135,131 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
WO 2005/047706 |
|
May 2005 |
|
WO |
|
WO 2006/061558 |
|
Jun 2006 |
|
WO |
|
Other References
International Search Report for corresponding International Patent
Application No. PCT/US2013/038589 dated Mar. 4, 2014. cited by
applicant.
|
Primary Examiner: Laurenzi; Mark
Assistant Examiner: Wan; Deming
Attorney, Agent or Firm: Merchant & Gould P.C.
Parent Case Text
This application is is a National Stage Application of
PCT/US2013/038589, filed 29 Apr. 2013, which claims benefit of U.S.
Patent Application Ser. No. 61/640,330 filed on 30 Apr. 2012 and
which applications are incorporated herein by reference. To the
extent appropriate, a claim of priority is made to the above
disclosed applications.
Claims
The invention claimed is:
1. A positive displacement pump assembly comprising: a rotor
housing defining a rotor cavity; an end plate configured to at
least partially close one end of the rotor cavity; rotor shafts
extending through the rotor cavity; rotors supported on and fixed
to the rotor shafts, the rotors having axial ends with end faces
that face the end plate; a first pair of bearings rotatably
mounting and axially fixing the rotor shafts to the end plate such
that the position of the end plate with respect to the shafts is
fixed to control a clearance between the end plate and the end
faces of the rotors; and a second pair of bearings rotatably
mounting the rotor shafts to the rotor housing; wherein the end
plate is axially movable with the rotor shafts relative to the
rotor housing when the rotor shafts vary in axial length due to
thermal fluctuations to thereby reduce changes in an axial
clearance at the end faces; and wherein the end plate at least
partially defines at least one inlet into the rotor cavity.
2. The positive displacement pump assembly of claim 1, further
comprising a second axial clearance, wherein the rotor housing has
a midportion that defines the rotor cavity and further includes an
end portion fixed to the midportion and wherein the second axial
clearance is between the end plate and the end portion and varies
as the rotor shafts and the end plate move axially.
3. The positive displacement pump assembly of claim 2, wherein the
rotor shafts extend through the end plate into the end portion; and
further comprising: needle bearings between the rotor shafts and
the end portion.
4. The positive displacement pump assembly of claim 2, wherein the
rotor shafts have ends flush with a face of the end plate at the
second axial clearance.
5. The positive displacement pump assembly of claim 1, wherein the
end plate has stepped openings configured to receive the first pair
of bearings and the rotor shafts.
6. The positive displacement pump assembly of claim 1, wherein the
end plate has an outer perimeter with a portion shaped to follow
contours of an inner surface of the rotor housing.
7. The positive displacement pump assembly of claim 6, wherein
another portion of the outer perimeter of the end plate at least
partially defines the at least one inlet into the rotor cavity.
8. The positive displacement pump assembly of claim 1, wherein the
rotor shaft is a first material and the rotor housing is a second
material; and wherein the first and the second materials have
different rates of thermal expansion.
9. The positive displacement pump assembly of claim 1, further
comprising timing gears mounted on the rotor shafts, wherein the
timing gears are positioned on the rotor shafts opposite the first
pair of bearings and positioned outside the rotor cavity.
10. The positive displacement pump assembly of claim 1, wherein the
positive displacement pump assembly is configured as a supercharger
adapted to pump air.
11. The positive displacement pump assembly of claim 1, wherein
leakage of fluid through the axial clearance at the end faces is
minimized by minimizing the changes in the axial clearance as the
rotors vary in axial length due to the thermal fluctuations.
12. The positive displacement pump assembly of claim 1, wherein the
first pair of bearings rotatably mounting and axially fixing the
rotor shafts to the end plate is configured so that the end plate
moves axially with the rotor shafts relative to the rotor
housing.
13. A positive displacement pump assembly comprising: a rotor
housing defining a rotor cavity; an end plate configured to at
least partially close one end of the rotor cavity; rotor shafts
extending through the rotor cavity; rotors supported on and fixed
to the rotor shafts, the rotors having axial ends with end faces
that face the end plate; a first pair of bearings rotatably
mounting the rotor shafts to the end plate; and a second pair of
bearings rotatably mounting the rotor shafts to the rotor housing;
wherein the end plate is axially movable with the rotor shafts
relative to the rotor housing when the rotor shafts vary in axial
length due to thermal fluctuations to thereby reduce changes in an
axial clearance at the end faces; wherein the end plate at least
partially defines at least one inlet into the rotor cavity; wherein
the end plate has an outer perimeter with a portion shaped to
follow contours of an inner surface of the rotor housing; wherein
another portion of the outer perimeter of the end plate at least
partially defines the at least one inlet into the rotor cavity; and
wherein the at least one inlet includes a pair of inlets and
wherein the end plate has an extension configured to rest on the
inner surface of the rotor housing to separate the pair of
inlets.
14. A positive displacement pump assembly comprising: a rotor
housing having a midportion that defines a rotor cavity that
extends through the midportion; a rotor shaft defining an axis and
extending through the rotor cavity; a rotor supported by and fixed
to the rotor shaft for rotation about the axis, the rotor having an
axial end face; an end plate within the rotor housing at least
partially defining a fluid passage into an end of the rotor cavity;
and a bearing on the rotor shaft between the end plate and the
rotor shaft and configured so that the end plate is axially fixed
by the bearing relative to the rotor shaft such that the position
of the end plate with respect to the shaft is fixed to control a
clearance between the end plate and the axial end face of the
rotor, wherein the end plate moves axially with the rotor shaft
relative to the rotor housing due to thermal fluctuations.
15. The positive displacement pump assembly of claim 14, further
comprising: a second axial clearance; wherein the rotor housing
further includes an end portion fixed to the midportion of the
rotor housing; and wherein the second axial clearance is between
the end plate and the end portion and varies as the rotor shaft and
the end plate move axially.
16. The positive displacement pump assembly of claim 15, wherein
the rotor shaft extends through the end plate into the end portion;
and further comprising: a needle bearing between the rotor shaft
and the end portion.
17. The positive displacement pump assembly of claim 15, wherein
the rotor shaft has an end flush with a face of the end plate at
the second axial clearance.
18. The positive displacement pump assembly of claim 14, wherein
the end plate has a stepped opening configured to receive the
bearing and the rotor shaft.
19. The positive displacement pump assembly of claim 14, wherein
the end plate has an outer perimeter with a portion shaped to
follow contours of an inner surface of the rotor housing.
20. The positive displacement pump assembly of claim 19, wherein
another portion of the outer perimeter of the end plate at least
partially defines the fluid passage into the end of the rotor
cavity.
21. The positive displacement pump assembly of claim 14, wherein
the bearing is a first bearing and the axial end face of the rotor
is a first end face; and further comprising: a second bearing
between the rotor housing and the rotor shaft at an opposite end of
the rotor than the first bearing so that the rotor shaft is axially
fixed relative to the rotor housing at the second bearing.
22. The positive displacement pump assembly of claim 14, wherein
the rotor shaft is a first material and the rotor housing is a
second material; and wherein the first and the second materials
have different rates of thermal expansion.
23. The positive displacement pump assembly of claim 14, further
comprising: a second rotor shaft defining a second axis and
extending through the rotor cavity; a second rotor supported by and
fixed to the second rotor shaft for rotation about the second axis,
the second rotor having a second axial end face; and a second
bearing on the second rotor shaft between the end plate and the
second rotor shaft and configured so that the end plate is axially
fixed by the second bearing relative to the second rotor shaft and
thereby moves axially with the second rotor shaft relative to the
rotor housing due to the thermal fluctuations to thereby reduce
changes in a second axial clearance at the second axial end face of
the second rotor.
24. A positive displacement pump assembly comprising: a rotor
housing having a midportion that defines a rotor cavity that
extends through the midportion; a rotor shaft defining an axis and
extending through the rotor cavity; a rotor supported by and fixed
to the rotor shaft for rotation about the axis, the rotor having an
axial end face; an end plate within the rotor housing at least
partially defining a fluid passage into an end of the rotor cavity;
and a bearing on the rotor shaft between the end plate and the
rotor shaft and configured so that the end plate is axially fixed
relative to the rotor shaft and moves axially with the rotor shaft
relative to the rotor housing due to thermal fluctuations to
thereby reduce changes in an axial clearance at the axial end face
of the rotor; wherein the end plate has an outer perimeter with a
portion shaped to follow contours of an inner surface of the rotor
housing; wherein another portion of the outer perimeter of the end
plate at least partially defines the fluid passage into the end of
the rotor cavity; and wherein the end plate has an extension
configured to rest on the inner surface of the rotor housing to
separate the fluid passage into a pair of fluid passages.
25. A positive displacement pump assembly comprising: a rotor
housing that defines a rotor cavity having a first end; a first and
a second rotor shaft extending through the rotor cavity; a first
and a second rotor configured to rotate within the rotor cavity on
the first and second rotor shafts, respectively, each of the rotors
having a first end face and a second end face at opposite first and
second axial ends; an end plate positioned to at least partially
close the first end of the rotor cavity; a first pair of bearings
on the rotor shafts between the end plate and the rotor shafts and
configured so that the end plate is axially fixed by the bearings
relative to the rotor shafts such that the position of the end
plate with respect to the first and second rotor shafts is fixed to
control a clearance between the end plate and the rotor first and
second end faces, wherein the end plate moves axially with the
rotor shafts relative to the rotor housing; a second pair of
bearings on the rotor shafts between the rotor housing and the
rotor shafts and configured to prevent the first and second rotors
from moving axially relative to the rotor housing; and a first and
a second timing gear mounted on the first and second rotor shafts,
respectively, the timing gears adapted to coordinate rotational
movement of the first and second rotors, and the timing gears
positioned outside of the rotor cavity.
26. The positive displacement pump assembly of claim 25, wherein
the timing gears are positioned adjacent the second pair of
bearings.
Description
TECHNICAL FIELD
The present teachings generally include a positive displacement
pump assembly, such as a supercharger assembly for an engine.
BACKGROUND
Positive displacement pumps can be used to add fluid pressure under
certain operating conditions. A supercharger is one type of
positive displacement pump that is used to boost air pressure at an
engine air intake. Positive displacement air pumps typically have
meshing, multi-lobed rotors within a rotor housing. Air is moved
from an inlet to an outlet; clearance between the rotors and the
rotor housing is designed to prevent air from following unintended
paths. Air leakage around the rotor end faces is one unintended
path and a cause of positive displacement air pump
inefficiency.
The rotors are mounted on rotor shafts. The rotors and rotor shafts
may tend to expand and contract due to thermal fluctuations. The
rotor housing may also tend to expand and contract, and may do so
at different rates than the rotors or rotor shafts, especially if
formed from a different material. One solution has been to leave a
gap between the rotor face and the rotor housing at the inlet end
of the housing that is sufficiently large to allow the rotor shafts
and the housing to expand relative to one another. The rotor shafts
are typically fixed axially to the rotor housing at one end by
bearings, referred to herein as axial bearings. Needle bearings
between the rotor shafts and the rotor housing on the other end
allow the rotor shafts to expand and contract axially relative to
the rotor housing.
SUMMARY
A positive displacement pump assembly is provided that allows axial
expansion and contraction of rotors and rotor shafts relative to
the housing along the length of the rotor cavity while reducing a
change in axial clearance at faces of the rotors. The positive
displacement pump assembly includes a rotor housing defining a
rotor cavity, and an end plate configured to at least partially
close one end of the rotor cavity. Rotors are fixed to and
supported on rotor shafts and extend through the rotor cavity. A
first pair of bearings fixes the rotor shafts axially to the end
plate. A second pair of bearings fixes the rotor shafts axially to
the rotor housing, preventing relative axial movement between the
rotor shafts and the rotor housing. The end plate is axially
movable with the rotor shafts when the rotor shafts vary in axial
length due to thermal fluctuations so that changes in the axial
clearance at the end faces of the rotors due to thermal
fluctuations is substantially reduced. The effect of material
selection and associated thermal expansion rates of the rotors,
rotor shafts, and the rotor housing on the clearance is thus
significantly reduced, and leakage through the clearance will thus
be minimized with a corresponding increase in efficiency of the
positive displacement pump assembly.
The above features and advantages and other features and advantages
of the present teachings are readily apparent from the following
detailed description of the best modes for carrying out the present
teachings when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic cross-sectional illustration of a positive
displacement pump assembly taken at lines 1-1 in FIG. 5 in
accordance with one aspect of the present teachings.
FIG. 2 is a schematic perspective illustration of an axial end
plate of the positive displacement pump assembly of FIG. 1.
FIG. 3 is another schematic perspective illustration of the axial
end plate of FIG. 2.
FIG. 4 is a schematic perspective illustration of the positive
displacement pump assembly of FIG. 1, with an end portion of the
rotor housing removed.
FIG. 5 is a schematic perspective illustration of the positive
displacement pump assembly of FIG. 5, with the end portion attached
to a midportion of the rotor housing.
FIG. 6 is a schematic cross-sectional illustration of a positive
displacement pump assembly in accordance with another aspect of the
present teachings.
FIG. 7 is a schematic perspective illustration of an end plate of
the positive displacement pump assembly of FIG. 6.
FIG. 8 is a schematic perspective illustration of the positive
displacement pump assembly of FIG. 6 with the end portion of the
rotor housing removed.
DETAILED DESCRIPTION
Referring to the drawings, wherein like reference numbers refer to
like components throughout the several views, FIG. 1 shows a
positive displacement pump assembly 10. In this embodiment, the
positive displacement pump assembly 10 is a supercharger assembly
for an engine, although the positive displacement pump assembly 10
may be used to pump other fluids and in other applications. The
positive displacement pump assembly 10 has a first rotor 12 that
meshes with a second rotor 14. Each of the rotors 12, 14 has
multiple lobes. The first rotor 12 is mounted on and rotates with a
first rotor shaft 16. The second rotor 14 is mounted on and rotates
with a second rotor shaft 18 that is generally parallel with the
first rotor shaft 16.
The rotors 12, 14 and rotor shafts 16, 18 are contained within a
multi-component positive displacement pump housing 20. The housing
20 includes a front cover 22, a midportion 24 that can be referred
to as a rotor housing portion, and an end portion 26. The front
cover 22 and the end portion 26 are fastened with bolts or
otherwise secured to the midportion 24.
An input shaft 28 that can be driven by an engine belt or other
drive input is operatively connected to the first rotor shaft 16
through a coupling 30. A torsion spring 32 is connected at one end
to the front cover 22 of the positive displacement pump housing 20
and at another end to the input shaft 28. The torsion spring 32
damps vibrations of the input shaft 28. A first timing gear 34 is
mounted on and rotates with the first rotor shaft 16 and meshes
with a second timing gear 36 mounted on and rotating with the
second rotor shaft 18 to cause rotation of the second rotor shaft
18.
The midportion 24 defines a rotor cavity 38 through which the rotor
shafts 16, 18 extend and in which the rotors 12, 14 rotate. A fluid
such as air is driven through the rotor cavity 38 from an inlet 39
(shown in FIG. 5 and referred to herein as an air inlet) in the end
portion 26 to an outlet 42 in the midportion 24 (shown in hidden
lines in FIG. 5 and referred to herein as an air outlet). Air that
can be passed from the air inlet 40 to the air outlet 42 by passing
between the mesh of the rotors 12, 14, or air that exits out of the
rotor cavity 38 by passing back to the inlet 39 along first axial
end faces 40A, 40B of the rotors 12, 14 or along second axial end
faces 43A, 43B of the rotors 12, 14 is referred to as "leakage" and
decreases the efficiency of the positive displacement pump assembly
10. In order to minimize such leakage, changes in an axial
clearance 45 between the midportion 24 and the second end faces
43A, 43B due to thermal fluctuations, as well as changes in an
axial clearance 48 at the first end faces 40A, 40B due to thermal
fluctuations are minimized while the positive displacement pump
assembly 10 still accommodates axial expansion and contraction of
the rotors 12, 14 and rotor shafts 16, 18 relative to the rotor
housing 20 due to the thermal fluctuations.
Specifically, an end plate 44 is axially fixed for movement with
the rotor shafts 16, 18 by a first pair of bearings 46A, 46B
positioned between the rotor shafts 16, 18 and the end plate 44.
The bearings 46A, 46B are press fit into stepped openings 50A, 50B
in the end plate 44. The stepped openings 50A, 50B are best shown
in FIGS. 1 and 3. The bearings 46A, 46B are configured to permit
the rotor shafts 16, 18 to rotate relative to the end plate 44, but
fix the axial position of the rotor shafts 16, 18 relative to the
end plate 44. Changes in a first predetermined clearance 48 between
the first end faces 40A, 40B and a face 51 of the end plate 44
(best shown in FIG. 2) due to thermal fluctuations are thus
minimized. The clearance 48 is very small relative to the
surrounding components, and is indicated in FIG. 1 as a line at the
end faces 40A, 40B. A second axial clearance 52 between an internal
surface 54 of the end portion 26 and a face 56 of the end plate 44
can vary in size as the end plate 44 moves toward or away from the
surface 54 because the end plate 44 is not axially fixed to the
rotor housing 20. The surface 51 of the end plate 44 defines an end
58 of the rotor cavity 38.
A second pair of bearings 57A, 57B is positioned between the
midportion 24 and the rotor shafts 16, 18 and axially fixes the
rotor shafts 16, 18 to the midportion 24. The bearings 57A, 57B are
referred to herein as axial bearings. The bearings 57A, 57B are
press fit into stepped openings 59A, 59B of the midportion 24 near
second axial ends 65A, 65B of the rotor shafts 16, 18. The bearings
57A, 57B are configured to permit the rotor shafts 16, 18 to rotate
relative to the midportion 24, but fix the axial position of the
rotor shafts 16, 18 relative to the midportion 24. Seals 63A, 63B
are positioned around the rotor shafts 16, 18 in the stepped
openings 59A, 59B between the axial bearings 57A, 57B and the rotor
cavity 38. Oil can fill the stepped openings 59A, 59B around the
seals 63A, 63B, and the seals 63A, 63B prevent oil leakage into the
rotor cavity 38.
As the temperature of the positive displacement pump assembly 10
increases, the rotors 12, 14 and rotor shafts 16, 18 and the rotor
housing 20 may expand axially an amount dependent on the linear
thermal expansion coefficient of the materials from which they are
formed. Expansion of the rotors 12, 14, rotor shafts 16, 18 and
rotor housing 20 is also dependent on a temperature gradient that
may exist along the length of the rotors 12, 14 and the housing 20
due to the fact that compressed air (or other fluid) at the outlet
42 of the housing 20 is much hotter than the air (or other fluid)
at the inlet 39 of the housing 20. This may cause the ends 60A, 60B
of the shafts 16, 18 to move axially toward or away from the
surface 54 of the end portion 26, varying the clearance 52. The
width of the clearance 52 does not affect leakage of the positive
displacement pump assembly 10. By reducing variations of the
clearance 48, and instead allowing the width of the clearance 52 to
vary freely with the thermal fluctuations, the end plate 44 can
provide a high efficiency for the positive displacement pump
assembly 10.
In one nonlimiting example, the rotor shafts 16, 18 can be a first
material, such as steel, and the rotor housing 20 can be a second
material, such as an aluminum alloy. These materials have different
rates of linear thermal expansion and contraction, quantified as
coefficient of linear thermal expansion. For example, the
coefficient of linear thermal expansion of steel may be
13.times.10.sup.-6 meters per meter per degree Kelvin, while that
of Aluminum may be 22.2.times.10.sup.-6 meters per meter per degree
Kelvin, and that of an Aluminum alloy somewhere therebetween.
However, the end plate 44 is fixed to move axially with the rotor
shafts 16, 18 and so will significantly reduce variations in the
clearance 48 despite these different rates of expansion and
contraction. The end plate 44 can be the same material as the
rotors 12, 14 to best maintain the clearance 48.
FIGS. 2 and 3 show the unique shape of the outer perimeter 70 of
the end plate 44. A first portion 72 of the outer perimeter 70 is
shaped to follow the contours of an inner surface 74 of the rotor
housing 20. Specifically, the shape of the first portion 72 matches
the adjoined cylindrical cavities that form the rotor cavity 38 to
house the rotors 12, 14, and also matches a recess 75 in the end
portion 26 in which the end plate 44 is housed. The end plate 44
partially closes the open end of the midportion 24 to define the
end 58 of the rotor cavity 38. The end plate 44 is sized so that
the first portion 72 of the perimeter 70 can slide axially relative
to the inner surface of the end portion 26 at the recess 75 but
minimizes air leakage around the perimeter 70. The inner surface 74
of an alternative embodiment of the end portion 126 is shown in
FIG. 7. The end portion 126 has the same inner surface 74 as the
end portion 26.
A second portion 78 of the perimeter 70 shown in FIG. 2 partially
defines inlets 80A, 80B into the rotor cavity 38, referred to
herein as air inlets. The air inlets 80A, 80B are aligned with the
air inlet 40 in the end portion 26. The midportion 24 defines the
remainder of the air inlets 80A, 80B, as shown in FIG. 4. The inner
surface of the midportion 24 forms a support rib 82 that runs
axially along the rotor cavity 38 and partially separates the
adjoined cylindrical cavities of the rotor cavity 38. The inner
surface of the end portion 26 at the air inlet 40 has a support rib
83 that aligns with the support rib 82 when the end portion 26 is
fastened to the midportion 24. The end plate 44 has an extension 84
with a flared end 86 that is configured to conform to the shape of
the support rib 83. The support rib 83 helps to support the end
plate 44 within the end portion 26.
FIG. 6 shows a second embodiment of a positive displacement pump
assembly 110 that is the same as is described with respect to the
positive displacement pump assembly 10 except that rotor shafts
116, 118 and an end portion 126 of the positive displacement pump
housing 120 have a different configuration. Specifically, first and
second rotor shafts 116, 118 are used that extend into an end
portion 126 that has openings 90A, 90B. Ends 160A, 160B of the
rotor shafts 116, 118 extend beyond the end plate 44. The positive
displacement pump housing 120 includes the front cover 22, the
midportion 24 and the end portion 126. Needle bearings 92A, 92B are
supported in the openings 90A, 90B and surround the rotor shafts
116, 118. The rotor shafts 112, 118 are axially fixed relative to
the front cover 22 and an end portion 126 by both sets of the
bearings 57A, 57B and 46A, 46B. The needle bearings 92A, 92B allow
the rotor shafts 116, 118 to move axially relative to the end
portion 126 and function as an additional positional reference for
the rotor shafts 116, 118 with respect to the housing 120. The end
portion 126 and the end plate 44 define the clearance 52, and the
rotor end faces 40A, 40B and the face 51 of the end plate 44 define
the clearance 48 just as in the embodiment of the positive
displacement pump assembly 10.
The reference numbers used in the drawings and the specification
along with the corresponding components are as follows:
10 positive displacement pump assembly
12 first rotor
14 second rotor
16 first rotor shaft
18 second rotor shaft
20 positive displacement pump housing
22 front cover
24 midportion
26 end portion
28 input shaft
30 coupling
32 torsion spring
34 first timing gear
36 second timing gear
38 rotor cavity
39 inlet
40A, B first axial end faces
42 outlet
43A, B second axial end faces
44 end plate
45 clearance
46A, B first axial bearings
48 first axial clearance
50A, B stepped openings of end plate
51 face of end plate
52 second clearance
54 internal surface of end portion
56 face of end plate
57A, B second pair of axial bearings
58 end of rotor cavity
59A, B stepped openings in end portion
60A, B ends of rotor shafts
63A, B seals
65A, B second axial ends
70 outer perimeter of end plate
72 first portion of outer perimeter
74 inner surface of end plate
75 recess of end plate
78 second portion of outer perimeter
80A, B inlets
82 support rib of midportion
83 support rib of end portion
84 extension
86 flared end
90A, B openings in end portion 126
92A, B needle bearings
110 positive displacement pump assembly
116 first rotor shaft
118 second rotor shaft
120 positive displacement pump housing
126 end portion
160A, B ends of rotor shafts
While the best modes for carrying out the many aspects of the
present teachings have been described in detail, those familiar
with the art to which these teachings relate will recognize various
alternative aspects for practicing the present teachings that are
within the scope of the appended claims.
* * * * *